- Remove OS matrix from lint job; run lint only on ubuntu-latest
- Upgrade actions/setup-python from v4 to v5 with pip caching
- Replace snok/install-poetry and manual cache with pip-based setup
- Simplify tox.ini by using `deps = poetry` and `poetry run` consistently
- Remove redundant `skipsdist = true` and duplicated commands_pre blocks
- Drop deprecated safety JSON output and html coverage report